Screw pump



Aug. 3, 1965 A. A. ZALIS 3,198,582

SCREW PUMP Filed Sept. 12, 1962 A E A m xmwl 6 25 I2 33 I I7 47 I9ALBERT A. ZALIS INVENTOR.

w lmwzwgw United States Patent 3,198,582 SCREW PUMP Albert A. Zalis,Warren, Mass, assignor to Warren Pumps, Inc, Warren, Mass, a corporationof Massachusetts Filed Sept. 12, 1962, Ser. No. 223,106 Claims. (ill.3432-44) This invention relates to a screw pump and, more particularly,to apparatus arranged to produce a change in pressure and flow inmaterials having a high concentration of solid particles.

There are some materials which, because of the presence of largeparticles or pieces of solid material, are difficult to pump. Forinstance, in a paper mill, bulk wood chips have heretofore been handledby chain conveyors and similar handling equipment. A similar situationexists in the grain industries and in handling coal slurries. Theproblem which is common to all of these industries is that the largesolid particles, i.e., the wood chips, kernels of grain, large particlesof coal, jam in the actuating parts of the pump. The screw pump is, formany reasons, a very desirable type of pump to use in such applications,but the screw pumps of the prior art have suffered from the deficiencythat tough fibrous particles, such as wood chips, have a tendency to jambetween the screw surfaces; this may render the pump inoperative or mayabsorb a considerably higher amount of power in its operation than wouldotherwise be true. These and other difficulties of the prior art havebeen obviated in a novel manner by the present invention.

It is, therefore, an outstanding object of the invention to provide ascrew pump capable of handling materials having a high concentration oflarge solid particles.

Another object of this invention is the provision of a screw pump havingan axial discharge.

A further object of the present invention is the provision of a screwpump having a novel bearing mounting means for the screw shafts.

It is another object of the instant invention to provide a screw pumphaving an axial discharge in which the screw shaft bearings are mountedin the axial outlet passage without seriously impeding the flow ofmaterial.

It is a further object of the invention .to provide a screw pump havingits shaft hearings in the flow of material provided with a seal ofunusual effectiveness.

A still further object of this invention is the provision of a screwpump having shaft bearings which lie close to the flow of material andwhich are provided with means for preventing the entrance of materialinto the bearing surfaces.

It is a still further object of the present invention to provide a screwpump in which large fibrous particles will not jam between the screwsurfaces.

With these and other objects in view, as will be apparent to thoseskilled in the art, the invention resides in the combination of partsset forth in the specification and covered by the claims appendedhereto.

The character of the invention, however, may be best understood byreference to one of its structural forms, as illustrated by theaccompanying drawings in which:

FIG. 1 is a perspective view of a pump embodying the principles of thepresent invention;

FIG. 2 is a horizontal sectional view of the pump taken on the line11-11 of FIG. 1; and

FIG. 3 is a vertical sectional view of the invention taken on the lineTil-III of FIG. 2.

Referring first to FIG. 1, wherein are best shown the general featuresof the invention, the screw pump, indicated generally by the referencenumeral It is shown as having an elongated body 11 which is formed infour parts, namely, a gear box 12, a bearing portion 13, a main portion14, and a discharge portion 15. Extending upwardly from the main portion14 of the body adjacent the bearing portion 13 is an inlet opening 16surrounded by a flange 17 by which it may be connected to a conduit. Thedischarge portion 15 is generally tubular; it is provided on its inboardend with a flange 18 by which it is attached to the main portion 14 andat its outboard end with a flange 19 by which it may be attached to aconduit. Extending from the gear box 12 is a drive shaft 21 which isadapted to be attached to a drive motor, not shown. The main body isSupported by two legs 22 and 23 which extend downwardly from oppositeends of the main portion 14. part of the discharge portion 15 and isconnected at its outer end to a source (not shown) of lubricant underpressure.

Referring now to FIGS. 2 and 3, it can be seen that the gear box 12 isprovided with a cover 25 from which the drive shaft 21 extends. A ballbearing 26 is carried in the gear box to hold the shaft 21, while aroller bearing 27 mounted in the bearing portion 13 also supports theshaft. A suitable seal 28 is mounted in the cover 25 around the driveshaft 21. Keyed to the drive shaft Within the gear box is a pinion gear29 which meshes with two gears 31 and 32. The gears 31 and 32 aremounted, respectively, on the shafts 33 and 34 which carry the mainscrews 35 and 36 of the pump. The shaft 33 is supported in a bearing 37located in the gear box 12 and a bearing 38 located in the bearingportion 13, the bearing holding the shaft on either side of the gear 31.The bearing portion 13 is provided with a stufling box 39 whichsurrounds the shaft 33 as it leaves the bearing portion 13 and entersthe main portion 14. Mounted on the shaft 33 under the inlet opening 16is a special feed screw 41. The feed screw 41 and the main screw 35 areheld axially tightly together on the shaft 33 by a pressure nut 42.Similarly, the shaft 34 is provided with a stulfing box 43 and a feedscrew 44. The main feed screws rotate in the same direction, as isevident from the drive arrangement in the gear box 12. They are of aspecial configuration (dictated by the geometry of two screw surfaceswhich rotate in the same direction) to provide very excellent pumpingsealing action. From the nature of such conjuga-te action there is neverany instant when two surfaces portion 15 and then decreases in diameterto a circular outlet opening 46. Extending vertically across the largestdiameter of the chamber are two pedestals 47 and 48 associated with theshafts 33 and 34, respectively. The pedestal 47 consists of an upperportion 49, a central portion 51, and a lower portion. The upper portion49 and the lower portion are streamlined in the direction ofmaterialfiow; that is to say, they are narrow in the transverse direction andelongated in the axial direction. The upper and lower portions serve tosupport the central portion 51 which is generally in the form of a hubor cylinder with its axis in the direction of the axes of the shafts.The pedestal 48 is similarly formed.

The central portion 51 is provided with a longitudinal bore 53 in whichis mounted a bearing sleeve 54 which carries a reduced portion 55 of theshaft 33. The conduit 24- carrying high pressure lubricant is attachedto a pas- A conduit 24 is connected to the upper central a) sage 56which extends radially inwardly from the upper part of the dischargeportion 15 through the upper portion 49 of the pedestal 47 and throughthe sleeve 54. A cover 57 is bolted to the downstream side of thecentral portion 51 of the pedestal 47 and covers the ends of the bolt53, the sleeve 54, and the reduced portion 55 of the shaft.

On the shaft 33 adjacent the pedestal 47 on the upstream side is mounteda sealing ring 58. This ring is provided with a generally frusto-conicalouter surface 59 which serves as a transition between the cylindricalsurface of the hub of the screw 35 and the outside diameter of thecentral portion 51 of the pedestal 47. The central portion of thepedestal is provided with an annular axial groove 61 in which lies anannular axial flange 62 formed on the ring 58. The groove and flange fittogether very tightly to provide a labyrinth from the main pumpingpassages into the mating bearing surfaces between the sleeve 54 and thereduced portion 55 of the shaft 33. A taper pin 63 extends through thehub of the main screw 35 and acts as a stop against which the main screw35 and the feed screw 41 may be tightly pressed by means of the pressurenut 42. The pedestal 48 is provided in its central portion with asimilar sealing ring 64 and the hub of the main screw 36 is providedwith a taper pin 65. It should be noted that the sealing ring 58 islocked to the shaft 33 by a key 66 so that it rotates with the shaft andis not fixed to the pedestal 47. Furthermore, the inside bore of thering 58 is the same size as the main part of the shaft 33 and thejunction between the main portion of the shaft and the reduced portion55 lies within the ring. The sleeve 54 is long enough to extend into thering 58 and abut against the shoulder between the main portion of theshaft 33 and the reduced portion'55.

The operation of the pump will now be readily understood in view of theabove description. Material to be pumped enters the pump through theinlet opening 16 from a conduit to which the flange 17 has been bolted.The material flows vertically onto the feed screws 41 which are of asufiicient coarseness, strength, and lead to cause the material to flowtoward the main screws 35 and 36. The material is picked up by the mainscrews and flows longitudinally through the body 11, eventually leavingthe ends of the main screws 35 and 36. The material flows into thechamber 45 and flows around the pedestals 47 and 48, finally leavingthrough the outlet opening 46 into a conduit which has been bolted tothe flange 19. Since the material may contain a liquid of a corrosivenature and since the solids may consist of abrasive particles, it isimportant that none of this material enter the bearings around theshafts 33 and 34. At the inlet end of the pump, the stufling boxes 39and 43 prevent the material from leaving around the shafts in thatdirection. Furthermore, the bearing portion 13 is provided with verticalpassages so that the shafts are exposed to the atmosphere and anymaterial leaking out of the stuffing box area will fall to the exteriorof the pump. It will not be carried into the hearings on which the inletends of the shafts are carried. At the exit end, the material isprevented from entering the bearing surface between the reduced portion55 of the shaft 33 and the bearing sleeve 54 on the upstream sidebecause of the presence of the sealing ring 58. Material would have toenter at the dividing line between the pedestal 47 and the sealing ring58, go around the labyrinth provided by the flange 62 and the groove 61,reverse its direction to go around the end of the sleeve 54 which liesin the center of the sealing ring, flow radially along the shoulderbetween the main part of the shaft 33 and the reduced portion 55 beforearriving at the bearing surfaces. On the other hand, the lubricant caseof a water slurry, the lubricant selected would prob ably be water. Inthe case where wood chips are being pumped, water could also be used asa lubricant since it would not affect the nature of the chips. On thedownstream side there can be no admittance to the hearing because of thesolid cover 57 in the case of the pedestal 47 and a similar cover 67 inthe case of the pedestal 48. Where the material contains large fibrousparticles, such as would be the case when pumping wood chips, the natureof the screws, whereby they rotate in the same direction and have nosurfaces which are come together, makes it impossible for such particlesto be pinched and to jam the pump. The power which must be transmittedinto the pump through the drive shaft 21 is, therefore, much lower thanwould otherwise be necessary. It will be understood that the crosssectional area of the chamber 45 from one end to the other, that is tosay, from its beginning at the end of the main screws 35 and 36 to itstermination at the outlet opening 46, is selected to be substantiallythe same. In the area of the pedestals 47 and 43 the cross-sectionalarea is selected so that when the transverse pedestal area is subtractedfrom the main area of the chamber the available flow area issubstantially the same as the cross-sectional area in the open parts ofthe passage.

Minor changes may be made in the form and construction of the inventionwithout departing from the material spirit thereof. It is not, however,desired to confine the invention to the exact form herein shown anddescribed, but it is desired to include all such as properly come withinthe scope claimed.

The invention having been thus described, what is claimed as new anddesired to secure by Letters Patent is:

1. A screw pump for materials containing a high concentration of solidparticles, comprising (a) an elongated body,

(b) two shafts extending through the body,

(c) means connecting the shafts for rotation in the same direction,

(d) a pumping screw associated with each shaft,

(e) an inlet opening in the body adjacent the screws at one end of thebody,

(f) an outlet passage in the body extending coaxially of the screws atthe other end of the body,

(g) a pedestal for each shaft extending across the outlet passage, thepedestal being streamlined and without flat surfaces facing upstream inthe direction of the axes of the shafts, and

(h) a bearing mounted in each pedestal and carrying one of the shafts.

2. A screw pump for material containing a high concentration of solidparticles, comprising (a) an elongated body,

(b) two shafts extending through the body,

(c) means connecting the shafts for rotation in the same direction,

(d) a pumping screw associated with each shaft,

(e) an inlet opening in the body adjacent the screws at one end of thebody,

(f) an outlet passage in the body extending coaxially of the screws atthe other end of the body,

(g) a streamlined pedestal for each shaft extending across the outletpassage,

(h) a bearing mounted in each pedestal and carrying one of the shafts,and

(i) means associated with the bearing to supply it with a lubricantunder pressure, which lubricant is com- A patible with the materialbeing pumped.

3. A screw pump for materials containing a high concentration of solidparticles, comprising (a) an elongated body,

(b) two shafts extending through the body,

(0) means connecting the shafts for rotation in the same direction,

(d) a pumping screw associated with each shaft,

(e) an inlet opening in the body adjacent the screws at one end of thebody,

(f) an outlet passage in the body extending coaxially of the screws atthe other end of the body,

(g) a streamlined pedestal for each shaft extending across the outletpassage,

(h) a bearing mounted in each pedestal and carrying one of the shafts,

(i) an annular axial groove formed in the pedestal around the bearing,and

(j) a sealing member mounted on a shaft and having an annular ridgewhich fits tightly in the said annular groove.

4. A screw pump for materials containing a high concentration of solidparticles, comprising (a) an elongated body,

(b) two shafts extending through the body,

(c) means connecting the shafts for rotation in the same direction,

(d) a pumping screw associated with each shaft,

(e) an inlet passage in the body extending vertically above the screwsat one end of the body,

(f) an outlet passage of generally circular cross-section in the bodyextending coaxially of the screws at the other end of the body,

(g) two pedestals extending vertically across the outlet passage, thepedestal being streamlined and without flat surfaces facing upstream inthe direction of the axes of the shafts,

(h) a bearing mounted in each pedestal and carrying one of the shafts,each pedestal consisting of a central enlarged portion in which thebearing is mounted and two narrow convecting portions extending inopposite directions from the enlarged portion to the surface of thepassage,

(i) means associated with the bearing to supply it with a lubricantunder pressure, which lubricant is compatible with the material beingpumped,

(j) an annular axial groove formed in the enlarged portion of eachpedestal around each bearing, and

(k) a sealing member mounted on each shaft and having an annular ridgewhich fits tightly in the said annular groove.

5. A screw pump for materials containing a high concentration of solidparticles, comprising (a) an elongated body having an inlet at one end,

(13) two shafts extending through the body,

(c) means connecting the shafts for rotation in the same direction,

(d) a pumping screw associated with each shaft,

(e) an outlet passage in the body extending coaxially with the screws atthe other end of the body, from the discharge end of the screws to anoutlet opening in the body,

(f) a streamlined pedestal for each shaft extending across the outletpassage, and

(g) a bearing mounted in the pedestal and carrying one of the shafts,the passage being enlarged in the vicinity of the pedestals so that theunrestricted area at that point is substantially the same as the area ofthe outlet opening.

References Cited by the Examiner UNITED STATES PATENTS 1,762,708 6/30Allred 103-89 2,448,745 9/ 48 Struckmann 302-50 2,924,181 2/60 Sonnet103-128 3,060,512 10/62 Martin et a1.

SAMUEL F. COLEMAN, Primary Examiner.

LAURENCE V. EFNER, Examiner.

1. A SCREW PUMP FOR MATERIAL CONTAINING A HIGH CONCENTRATION OF SOLIDPARTICLES, COMPRISING (A) AN ELONGATED BODY, (B) TWO SHAFTS EXTENDINGTHROUGH THE BODY, (C) MEANS CONNECTING THE SHAFTS FOR ROTATION IN THESAME DIRECTION, (D) A PUMPING SCREW ASSOCIATED WITH EACH SHAFT, (E) ANINLET OPENING IN THE BODY ADJACENT THE SCREWS AT ONE END OF THE BODY.(F) AN OUTLET PASSAGE IN THE BODY EXTENDING COAXIALLY OF THE SCREWS ATTHE OTHER END OF THE BODY, (G) A PEDESTAL FOR EACH SHAFT EXTENDINGACROSS THE OUTLET PASSAGE, THE PEDESTAL BEING STREAMLINED AND WITHOUTFLAT SURFACES FACING UPSTREAM IN THE DIRECTION OF THE AXES OF THESHAFTS, AND (H) A BEARING MOUNTED IN EACH PEDESTAL AND CARRYING ONE OFTHE SHAFTS.